DON EMMERT/AFP/Getty Images(NEWTOWN, Conn.) -- As the families of the 27 people killed in Friday's shooting at a Connecticut elementary school continue to cope with their loss, investigators continue to try to piece together just exactly what happened at the school.

On Saturday morning, Lt George Sinko of the Newtown, Conn. Police Department said the process of removing some of the bodies from the scene has begun.

Twenty children died Friday when a heavily armed man invaded a Newtown, Conn., elementary school, after killing his mother at her home and driving to Sandy Hook Elementary and spraying the school with bullets.

Lt Paul Vance said 18 children died in the school and two more died later in a hospital. Six adults were also slain, bringing the total to 26.

The gunman, identified as Adam Lanza, 20, killed himself inside of the school.

Late Friday, police said Nancy Lanza's body was found in the family home. According to sources, Lanza shot his mother in the face.

Sinko told ABC News that Adam Lanza appeared to have gained access to the school by breaking a glass window near a front door.

"Appears to be the case right now that that is how he gained entry into the school, but still investigating."

Adam Lanza was "obviously not well," a relative told ABC News.

Family friends in Newtown also described the young man as troubled and described his mother Nancy as very rigid. "[Adam] was not connected with the other kids," said one friend.

The FBI investigation into the shooting now spans at least three states -- New Jersey, Connecticut and Massachusetts -- with investigators interviewing relatives and friends of the elementary school gunman, ABC News has learned.

Sources told ABC News that Ryan, 24, works as a senior person in Ernst and Young's tax practice in Manhattan.

"He's a tax guy and he is clean as a whistle," a source familiar with his work said.

Ryan has worked at the firm four years.

There are no records showing that Nancy Lanza or Adam Lanza worked for the school, according to Janet Robinson, Superintendent of Newtown schools. She said it is possible Nancy “volunteered” or was a “substitute teacher.”

Officials were interviewing Ryan and his father, but neither person was under any suspicion, multiple sources said.

Sources said the shooter was armed with a Glock semi automatic handgun and a Sig Sauer semi automatic handgun, law enforcement sources told ABC News. Additionally, .223 caliber shell casings--a rifle caliber--were also found at the scene. He was wearing a bullet-proof vest when he opened fire in the elementary school.

First grade teacher Kaitlin Roig, 29, locked her 14 students in a class bathroom and listened to "tons of shooting" until police came to help.

"It was horrific," Roig said. "I thought we were going to die."

She said that the terrified kids were saying, "I just want Christmas…I don't want to die. I just want to have Christmas."

A tearful President Obama said there's "not a parent in America who doesn't feel the overwhelming grief that I do."

The president had to pause to compose himself after saying these were "beautiful little kids between the ages of 5 and 10." As he continued with his statement, Obama wiped away tears from each eye.

He has ordered flags flown as half staff.

The alert at the school ended when Vance announced, "The shooter is deceased inside the building. The public is not in danger." The massacre prompted the town of Newtown to lock down all its schools and draw SWAT teams to the school, authorities said Friday. Authorities initially believed that there were two gunmen and were searching cars around the school, but authorities do not appear to be looking for another gunman.

It is the second worst mass shooting in U.S. history, exceeded only by the Virginia Tech shooting in 2007 when 32 were killed before the shooter turned the gun on himself. Friday's carnage exceeds the 1999 Columbine High School shooting in which 13 died and 24 were injured.